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The Internet is a global system of interconnected computer networks that use

the standard Internet Protocol Suite (TCP/IP) to serve billions of users

worldwide.

It is a network of networks that consists of millions of private, public,

academic, business, and government networks, of local to global scope, that

are linked by a broad array of electronic, wireless and optical networking

technologies.

The Internet carries a vast range of information resources and services, such

as the inter-linked hypertext documents of the World Wide Web (WWW) and

the infrastructure to support electronic mail.

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ROLE OF INTERNET

Linking consumers and businesses via internet.

Monitoring/maintaining customer's Web sites.

Network management/systems integration.

Backbone access services for other ISP's.

Managing online purchase and payment systems.

Benefits of Internet:

Doing fast business.Trying out new ideas.

Gathering opinions.

Allowing the business to appear alongside other established businesses.

Improving the standards of customer service/support resource.

Supporting managerial functions.

Limitations:

Security

Privacy Threats: Hackers, viruses etc.

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INTRANET

An intranet is the generic term for a collection of private computer

networks within an organization.

The intranet is to the internal system of the organization what the internet is

to its external environment.

That is it links internal data networks of the company but prevents access to

other outside the company. It also facilitates data gathering from with the

company.

For example surveys can be easily conducted through the intranet to assess

employee moral or popularity of benefit packages.

Ford's intranet success is so spectacular that the automaker's in-house

website could save billion dollars and fulfill a cherished dream of buildingcars on demand

By opening up its intranet to suppliers and coordinating the delivery and

assembly of thousands of components some auto companies tried to move

closer to manufacturing on demand.

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1

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orkforce productivity:Intranets can also help users to locate and view information faster and use

applications relevant to their roles and responsibilities. With the help of a web

browser interface, users can access data held in any database the

organization wants to make available, anytime and - subject to security

provisions - from anywhere within the company workstations, increasing

employees' ability to perform their jobs faster, more accurately, and with

confidence that they have the right information. It also helps to improve the

services provided to the users.

2.Time:

With intranets, organizations can make more information available to

employees on a "pull" basis (i.e., employees can link to relevant information at

a time which suits them) rather than being deluged indiscriminately by emails.

3.Business operations and management:

Intranets are also being used as a platform for developing and deploying

applications to support business operations and decisions across the inter

networked enterprise

ROLE OF INTRANET

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EXTRANET

An extranet is a private network that uses Internet protocols, network

connectivity, and possibly the public telecommunication system to securely

share part of an organizations information or operations with suppliers,

vendors, partners, customers or other businesses.

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ROLE OF EXTRANET

1. Large Volume Data Exchange

2. Information Sharing

3. Collaboration

4. Synchronized Training

5. Service co-access

6. Exclusive Info Sharing

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INTERNET, INTRANET AND EXTRANET

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Telecommunication Media

Telecommunication is the transmission of information, over significant

distances, for the purpose of communication.

In earlier times, telecommunications involved the use of visual signals, such

as beacons, smoke, semaphore telegraphs, signal flags, and optical

heliographs, or audio messages via coded drumbeats, lung-blown horns,

or sent by loud whistles, for example.

In the modern age of electricity and electronics, telecommunications now also

includes the use of electrical devices such as telegraphs, telephones, and

teletypes, the use of radio and microwave communications, as well as fiber

optics and their associated electronics, plus the use of the orbiting satellites

and the Internet.

A telecommunication network is a collection of transmitters, receivers, and

telecommunication channels that send messages to one another. Some digital

communications networks contain one or more routers that work together to

transmit information to the correct user. An analog communications network

consists of one or more switches that establish a connection between two or

more users

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Telecommunication media include twisted-pair wire, coaxial cable, and

fiber optic cables. Also included are terrestrial microwave, communications

satellite, cellular phone systems, and packet and LAN radio.

Twisted Pair wire- Ordinary telephone wire consisting of copper wire twisted

into pairs is the most widely used medium for communication.

Coaxial cable- consists of a sturdy copper or aluminium wire wrapped with

spacers to insulate and protect it. They allow high speed data transmission.And are used instead of twisted pair wire lines in high service metropolitan

areas.

Fiber Optics uses cables consisting of one or more hair thin filaments or glass

fiber wrapped in a protective packet.

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Wireless Technologies

Wireless telecommunication technologies rely on radio wave, microwave,

Infrared and visible light pulses to transport digital communications withoutWires between communication device. This includes terrestrial microwave,

communication satellite cellular and PCS telephone and pager systems,

mobile data radio, wireless LANs and various wireless internet technologies.

Terrestrial microwave involves earthbound microwave systems that transmit

high speed radio signals in a line of sight path between relay stations spaced30miles apart.

Communication satellite also use microwave radio as their telecommunication

medium.

Cellular and PCS telephone and pager system use several radiocommunication technologies.

Wireless access to the internet , intranet and extranet is growing as more.

Web enabled information appliances proliferate, smart telephones, pagers,

PDAs and other portable communication devices

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Telecommunication Processors

Telecommunication processors such as modems, multiplexers, switches and

routers perform a variety of support functions between the computer and otherdevices in a telecommunications network.

Modems- are the most common type of communication processor. They convert

the digital signals from a computer or transmission terminal at one end of a

communications link into analog frequencies that can be transmitted over

ordinary telephone lines.

Multiplexers- is a combinations processor that allows a single communications

channel to carry simultaneous data transmissions from many terminals. This is

accomplished in two ways. In FDM a multiplexer divides high speed channel into

slow speed channels.

In TDM the multiplexer divides the time each terminal can use the high speedline into very short time slots.

Internetwork processors networks are interconnected by special purpose

communication processors called internetwork processors such as switches,

routers, hubs and gateways. A switch is a communications processor that makes

connections between telecommunications circuit in a network.

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Telecommunications software is a vital component of all telecommunication

networks.

For e.g mainframe based wide area networks frequently use telecommunicationsMonitors, CICS for IBM mainframe is a typical example.

Telecommunication software packages provide a variety of communications

support services. Network management packages such as L AN network

operating systems and WAN telecommunication monitors determinetransmission

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Network Topologies

There are several types of network topologies in telecommunication network.

A star network ties end user computers to a central computer.

A ring network ties local computer processors together in a ring.

A bus network is a network in which local processors share the same bus.

Client/sever networks may use a combination of star, ring and bus approaches.

Obviously the star network is more centralized while ring and bus networks have

a more decentralized approach.

Ring and bus networks are most common in LAN network. Ring network are

most reliable and less costly for such networks.

The physical topology of a network refers to the configuration of cables,

computers, and other peripherals. Physical topology should not beconfused with logical topology which is the method used to pass

information between workstations

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BUS NETWORK-

Advantages of a LinearBus Topology-

Easy to connect a computer or peripheral to a linear bus.

Requires less cable length than a star topology.Disadvantages of a LinearBus Topology

Entire network shuts down if there is a break in the main cable.

Terminators are required at both ends of the backbone cable.

Difficult to identify the problem if the entire network shuts down.

Not meant to be used as a stand-alone solution in a large building.

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STAR NETWORK-

Advantages of a Star Topology

Easy to install and wire.

No disruptions to the network when connecting or removing devices.

Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

Requires more cable length than a linear topology.

If the hub, switch, or concentrator fails, nodes attached are disabled.

More expensive than linear bus topologies because of the cost of the hubs,

etc.

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RING NETWORK-

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Advantages

Data is quickly transferred without a bottle neck. (very fast, all data traffic is in

the same direction)

The transmission of data is relatively simple as packets travel in one direction

only.

Adding additional nodes has very little impact on bandwidth

It prevents network collisions because of the media access method or

architecture required.

-Disadvantages

Data packets must pass through every computer between the sender and

recipient therefore this makes it slower.

If any of the nodes fail then the ring is broken and data cannot be transmitted

successfully.It is difficult to troubleshoot the ring.

Because all stations are wired together, to add a station you must shut down

the network temporarily.

In order for all computers to communicate with each other, all computers must

be turned on.

Total dependence upon the one cable

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OSI MODEL AND TCP/IP MODEL

The ISO has developed a seven layer Open

Systems Interconnection model to serve as

a standard model for network architecture.

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TCP/IP is internet protocol suite. It consists of five layers of protocol that can be

related to the seven layers of the OSI architecture.

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Application layer provides communications services for end user applications.

Presentation layer provides appropriate data transmission formats and codes.

Session Layer supports the accomplishment of telecommunication sessions.

Transport Layer supports the organization and transfer of data between nodes

In the network.

Network layer provides appropriate routing by establishing connections among

Network link.

Supports error free organization and transmission od data in the network.

Provides physical transmission of data on the telecommunication media in the

network.